MOLECULAR ANALYSIS OF HINDBRAIN DEVELOPME NT

Hindbrain development involves a segmentation process which in particu lar governs cranial-motor nerves organization. We have initiated a mol ecular analysis of this morphogenetic process by searching for genes e xpressed in specific hindbrain segments (rhombomeres). We have identif ied a gene encoding a transcription factor, Krox-20, which is specific of rhombomeres 3 and 5 and several genes encoding receptor tyrosine k inases which are also segment-specific. The study of Krox-20 has allow ed the identification of its nucleotide target, the localization of th e functional domains of the protein and the demonstration of its invol vement in the transcriptional activation of the Hoxb-2 gene and in the control of normal hindbrain development.